[gmx-users] (no subject)

[Erik Lindahl]

Hi,

1. You are comparing two different dihedrals. One is specifically for 
the atoms CA-CA-C-N, while the other one is a wildcarded type - they 
are NOT necessarily identical.

2. The dihedrals in amber are probably for the old version of 
united-atom OPLS.... Even the OPLS-AA values changed a bit between 1996 
(first publication) and 2002.

In general, we'd definitely look into it if there are any discrepancies 
with the published numbers of OPLS-AA/L (although I've already checked 
that pretty carefully), but I don't have time to debug amber :-)

Cheers,

Erik

On Mar 31, 2004, at 2:30 PM, Nikita Polyakov wrote:

> Hello all!
> I'm trying to convert Amber dihedral constants to ffoplsaabon.itp.
> I took opls_parm.dat from Amber7 force field and extact that line for 
> try:
>  X -CK-CB-X    4    5.3        180.              2.  Supposed dihedral 
> is:
>  C2=-5.565
> In that case probably C0 = -C2 = 5.565. So C1=C3=C4=C5=0
> X      CA     C      X       3      5.565     0.00000   5.565    
> 0.00000   0.00000   0.00000   But in ffoplsaabon.itp for example:
> CA     CA     C      N       3      4.60548   0.00000  -4.60548  
> 0.00000   0.00000   0.00000 ; benzamide  Could you explain difference 
> or where I did mistake?
>   Nikita Polyakov, MSU student.
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